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Direct composite resin restoration of a class IV fracture by using 3D printing technology: A clinical report

Direct composite resin restoration of a class IV fracture by using 3D printing technology: A clinical report



Direct composite resin restoration of a class IV fracture by using 3D printing technology: A clinical report




Journal of Prosthetic Dentistry, 2021-04-01, Volume 125, Issue 4, Pages 555-559, Copyright © 2020 Editorial Council for the Journal of Prosthetic Dentistry


Abstract

Mimicking the appearance of the adjacent natural tooth is challenging when restoring a fractured anterior tooth. This clinical report describes a modified index technique for restoring a class IV defect. A replica of the restored tooth was fabricated with computer-aided design and 3D printing technology, which precisely mimicked the contralateral incisor. Labial and lingual silicone indices were developed on the replica to transfer the designed contour to the tooth to achieve a highly esthetic and precise restoration.

Direct composite resin restorations can be used to replicate the appearance of natural teeth; however, the technique requires practice and skill. To achieve optimal esthetics of a restored fractured anterior tooth, color, anatomy, translucency, occlusion, and smile line curvature should be taken into consideration. In restorations of class IV fractures with a large lingual defect, clinicians often use diagnostic waxing or trial restorations, from which a silicone index is created to help shape the palatal surface of the restoration. However, when diagnostic waxing or placing a trial restoration, it is difficult to match a single contralateral tooth and to develop optimal occlusal contacts.

By using computer-aided design (CAD) technology, a geometrically modeled item can be examined from any direction. This model can then be used for multiple applications such as manufacturing and analysis. Rapid prototyping (3D printing) can divide a scanned digital model into layers and then stack them into solid casts layer by layer. Both techniques have been widely used in multiple fields, including mandibular reconstruction in oral surgery, dental implant guides, and guides for endodontic treatment and periapical surgery. This clinical report describes the use of a modified index technique on a class IV defect to provide an esthetic, direct anterior restoration by using intraoral scanning, CAD modeling, 3D printing, silicone indices, and a layered restoration technique.


Clinical report

A 32-year-old man presented with a fractured maxillary left central incisor from trauma 1 month previously. A clinical examination revealed a horizontal fracture in the dentin, without pulpal exposure or root fracture ( Fig. 1 A, 1 B ). Both maxillary central incisors exhibited a combination of white crazing, brown stains on the marginal ridge, and a brown-stained enamel microcrack on the cervical part. The patient sought a highly esthetic restoration of the fracture.

Initial clinical situation. A, Fractured left maxillary central incisor. B, Periapical radiograph. C, Digital cast obtained from intraoral scan.
Figure 1
Initial clinical situation. A, Fractured left maxillary central incisor. B, Periapical radiograph. C, Digital cast obtained from intraoral scan.

Direct composite resin restoration by using a modified index technique was planned with the assistance of CAD and 3D printing technology. Briefly, after scanning the dentition by using an intraoral scanner (TRIOS 3; 3Shape A/S) ( Fig. 1 C), a digital diagnostic waxing was generated with dental CAD software (EXOCAD; exocad GmbH) by using the contralateral tooth as a reference ( Fig. 2 A, 2 B ). The occlusion on the digital restoration ( Fig. 2 C, 2 D) was adjusted to achieve precise occlusal contacts. After approval by the patient, the digital diagnostic waxing was exported as a standard tessellation language file and sent to a 3D printer (EvoDent; Union Tech GmbH) to create a replica of the restored tooth ( Fig. 3 A).

A, B, Frontal view of restoration design developed in dental CAD software. C, D, Occlusion optimized on digital restoration.
Figure 2
A, B, Frontal view of restoration design developed in dental CAD software. C, D, Occlusion optimized on digital restoration.

A, 3D-printed dentition. B, Enamel shade: UE3. C, Dentin shade: UD1. D, Dental dam isolation.
Figure 3
A, 3D-printed dentition. B, Enamel shade: UE3. C, Dentin shade: UD1. D, Dental dam isolation.

8The color shade was recorded as UE3 ( Fig. 3 B) for enamel and UD1 ( Fig. 3 C) for dentin (HRi; Micerium S.p.A). After dental dam isolation ( Fig. 3 D), the teeth were cleaned by using a small brush with a polishing agent (Proxyt RDA 36; Ivoclar Vivadent AG). Before restoration, lingual and labial silicone indices were fabricated on the 3D-printed replica by using polyvinyl siloxane putty (Virtual Putty; Ivoclar Vivadent AG) ( Fig. 4 A, 4 B ). A 1.5-mm, 45-degree enamel bevel was placed on the labial surface ( Fig. 4 C), and the lingual enamel was slightly recontoured with a flame-shaped diamond rotary instrument (TR-11; MANI Inc) and then polished with a coarse disk (Sof-Lex; 3M ESPE). After protecting the adjacent teeth with polytetrafluorethylene tape (PTFE Film Tape; 3M ESPE), the enamel was etched with 35% phosphoric acid (Eco-Etch; Ivoclar Vivadent AG) for 20 seconds, rinsed for 30 seconds, and gently dried. Universal adhesive (Single Bond Universal; 3M ESPE) was applied to the dentin and etched enamel and air-dried for 5 seconds before light polymerization (VALO Cordless; Ultradent Products, Inc).

A, Palatal index. B, Labial index. C, Esthetic enamel bevel on labial surface. D, E, F, Generation of palatal wall using palatal index. G, Completed dentine core. H, I, Generation of labial contour using labial index.
Figure 4
A, Palatal index. B, Labial index. C, Esthetic enamel bevel on labial surface. D, E, F, Generation of palatal wall using palatal index. G, Completed dentine core. H, I, Generation of labial contour using labial index.

Following the manufacturer’s instructions, the composite resin was heated before application (39 °C for UE, 55 °C for UD). The palatal index was loaded with a 0.5-mm-thick layer of UE3 enamel shade composite resin (HRi; Micerium S.p.A) and placed on the lingual surface of the tooth. The composite resin was then adapted to the lingual surface and polymerized ( Fig. 4 D-F). UD1 dentin shade composite resin (HRi; Micerium S.p.A) was used to build the dentin component ( Fig. 4 G) to a level approximately 1 mm higher than the incisal edge, 0.5 mm shallower than the surface, and covering half of the facial bevel. Each increment of composite resin was polymerized for 20 seconds.

A layer of UE3 enamel shade composite resin (HRi; Micerium S.p.A) was placed on the labial surface. Covered by antiadhesive polytetrafluorethylene tape, the labial index was placed against the tooth, and the labial surface anatomy was reproduced ( Fig. 4 H). After removing the polytetrafluorethylene tape ( Fig. 4 I), excess material was removed, and the composite resin was brushed toward the beveled facial surface to complete the transition ( Fig. 5 A).

A, Restoration before custom staining. B, C, Resin staining material printed on the restoration. D, Staining completed.
Figure 5
A, Restoration before custom staining. B, C, Resin staining material printed on the restoration. D, Staining completed.

To mimic the brown stain on the marginal edge, a transparent polyester strip (Hawe Stopstrip; KaVo Kerr Corp) was inserted between the incisors with a stop attached to the lingual side and the right incisor covered. The stain was traced on the strip using resin staining material (IPS Empress Direct Color; Ivoclar Vivadent AG) and transferred to the left incisor and polymerized. In this way, the brown stain on the right incisor was symmetrical to the left incisor ( Fig. 5 B, 5 C). A thin layer of UE3 composite resin was applied to cover the stain ( Fig. 5 D).

Carbide burs (Q series; Komet Dental) were used to refine the contour, texture, and microanatomy of the restoration. A flame-shaped diamond rotary instrument (FO-32; MANI Inc) was used to remove a minor occlusal interference on the lingual side. A hand instrument (LM-Arte Eccesso; LM-Instruments Oy) and diamond strip (Diastrips; Ernst Vetter GmbH) were used to eliminate interproximal excess. A dental polishing system (Diacomp plus twist; Ernst Vetter GmbH) was used for the definitive polishing steps. Figure 6 shows excellent replication of the contralateral tooth in both contour and color.

After treatment.
Figure 6
After treatment.

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